Evaluation of Circulating Markers of Neutrophil Extracellular Trap (NET) Formation as Risk Factors for Diabetic Retinopathy in a Case-Control Association Study

Background: Inflammatory stimuli can induce neutrophils to release nuclear DNA combined with histones into the extracellular space, forming neutrophil extracellular traps. Because inflammation contributes to diabetic retinopathy, it is plausible that neutrophil extracellular trap formation actively occurs in diabetic retinopathy. This case-control study investigated the clinical relevance of circulating levels of neutrophil extracellular trap components as risk factors of diabetic retinopathy, and further evaluated whether glucose induced neutrophil extracellular trap formation in vitro using whole blood from healthy volunteers. Methods: Circulating levels of DNA-histone complexes, cell free double-stranded DNA, and polymorphonuclear neutrophil elastase, considered to be markers of neutrophil extracellular trap formation, were measured in patients with diabetic retinopathy (n=28) and without (n=62) and in 28 healthy controls. Results: Circulating DNA-histone complex and polymorphonuclear neutrophil elastase levels were significantly increased in patients with diabetic retinopathy compared with those without retinopathy. Multivariable logistic regression analysis, adjusted for glycated hemoglobin levels and fasting blood glucose, revealed that DNA-histone complex and polymorphonuclear neutrophil elastase levels were significant independent risk factors of retinopathy. In vitro experiments also showed that glucose significantly increased markers of neutrophil extracellular trap formation in a dose-dependent manner. Conclusions: Markers of neutrophil extracellular trap formation were independent risk factors of diabetic retinopathy. This finding provides a new insight into the potential therapeutic and preventive approaches to dampen neutrophil extracellular trap formation.

Efficacy and safety of the dipeptidyl peptidase-4 inhibitor gemigliptin compared with sitagliptin added to ongoing metformin therapy in patients with type 2 diabetes inadequately controlled with metformin alone

AIMS

This study was designed to assess the efficacy and safety of a dipeptidyl peptidase-4 inhibitor, gemigliptin versus sitagliptin added to metformin in patients with type 2 diabetes.

METHODS

We conducted a double-blind, randomized, active-controlled trial in 425 Asian patients with inadequately controlled type 2 diabetes being treated with metformin alone. Eligible patients were randomized into three groups: 50 mg gemigliptin qd, 25 mg gemigliptin bid or sitagliptin 100 mg qd added to ongoing metformin treatment for 24 weeks. Haemoglobin A1c (HbA1c) and fasting plasma glucose (FPG) were measured periodically, and oral glucose tolerance tests were performed at baseline and 24 weeks after starting the treatment regimen.

RESULTS

Twenty-four weeks later, adding gemigliptin (50 mg/day) to ongoing metformin therapy significantly improved glycaemic control. Reduction in HbA1c caused by 50 mg gemigliptin qd (-0.77% ± 0.8) was non-inferior to that caused by 100 mg sitagliptin qd (-0.8% ± 0.85). Proportion of patients achieving HbA1c <7% while taking 25 mg gemigliptin bid (50%) or 50 mg gemigliptin qd (54.07%) was comparable to the results with 100 mg sitagliptin qd (48.87%). There were significant decreases in FPG, postprandial glucose and AUC0-2 h glucose, as well as increases in GLP-1 and β cell sensitivity to glucose (supported by homeostasis model assessment of β-cell function, postprandial 2-h c-peptide and insulinogenic index) in patients receiving gemigliptin treatment with their metformin therapy. There was no increased risk of adverse effects with this dose of gemigliptin compared with sitagliptin 100 mg qd.

CONCLUSIONS

Addition of gemigliptin 50 mg daily to metformin was shown to be efficacious, well tolerated and non-inferior to sitagliptin in patients with type 2 diabetes mellitus.